This invention relates to a kind of illuminator, or more specifically to a cold-end device of a low-pressure mercury vapor discharge lamp (DLLPMV).
It is well known that illumination of a DLLPMV is within the discharging area. The electronic energy level of Hg atom is transited to radiate ultra-violet rays, and then the fluorescent powder in the tube is excited to radiate visible lamp. The stronger the ultra-violet lamp is, the larger the light flux is. The intensity of the ultraviolet lamp is dependent on the density of the Hg atoms, i.e. it is related to the pressure of the mercury vapor. For a lamp tube with certain structure and power, an optimal value exists between the mercury vapor pressure value and the light flux value of the lamp. Therefore, it is critical to control the pressure of the mercury vapor to be within the optimal pressure.
The pressure of the mercury vapor in the lamp tube corresponds to the coldest point (generally named as cold-end) of the lamp in operation. To achieve the optimal light flux, measures must therefore be taken to decrease the temperature of the cold-end. The EC lamps available in the market, especially those with cover and those with large surface power load, usually have very high cold-end temperatures. For instance, the cold-end temperature of the 20 W EC lamp with cover is about 123 degree. The methods generally adopted in the world to decrease the cold-end temperature are to lengthen the exhaust pipe of the lamp tube to form a cold-end. As in FIG. 1, an extra segment 14 of exhaust pipe is added to the exhaust hole 18 made by the technology available currently, where 10 is the mercury alloy placed at the cold-end. When this cold-end device is applied to the integrated EC lamp, with all the components assembled on it, the cold-end in FIG. 1 seems to be at the center of the electronic ballast. The actual effect of this coldend device, however, is poor, i.e. the cold-end temperature fails to decrease due to the influence of its small volume and heating of the electronic components themselves. Moreover, the setting of this cold-end device is not good to the design assembly and the further reduction of its volume.
To well solve the above problems existing in the cold-end devices of EC lamps, especially those with cover and large surface power load, this invention is invented to provide a kind of cold-end device of a DLLPMV. The optimal cold-end temperature can be achieved, and hence a larger light flux of the working EC lamp can be achieved by adjusting the length and the position of the glass tube which is connected onto the cold-end.
The purpose of this invention is realized in such an way: A cold-end device of a DLLPMV of this invention, includes the external glass tube and mercury alloy placed in the glass tube as mentioned. Its feature lies in that the external glass tube of this model is connected to the wall of the lamp tube and is opened up to the inner room of the tube and thus isolated from the outside. The sealing end of the external glass tube fore-mentioned is far away from the heat source setting. It is preferable to place the sealing end near the top setting of the glass tube. Furthermore, the length of the external glass tube ranges from 5 mm to around two times of the lamp tube height (2H). When the external tube is long, U-shape is adopted for it; and when it is short, the shape similar to a bulb is adopted. However, L-shape is usually taken for it.
Its advantages and benefits are quite significant as compared with the prior art. Simply because the cold-end device of the model can be adjusted in the length of the external glass tube and the position of the sealing end of the glass tube, to be far away from heat source, the optimal cold-end temperature can be achieved, and hence a larger light flux of the EC lamp in operation can be output.